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package com.github.antelopeframework.mybatis.criterion;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.lang3.StringUtils;

import lombok.Getter;

/**
 * Criteria is a simplified API for retrieving entities by composing
 * Criterion objects. This is a very convenient approach for
 * functionality like "search" screens where there is a variable number of
 * conditions to be placed upon the result set.

 * 

 * The method Criteria.createCriteria() is a factory for
 * Criteria. Criterion instances are usually obtained via the
 * factory methods on Restrictions. eg.
 * 
 *  * Criteria criteria = Criteria.createCriteria(Cat.class)
 * 	.add(Restrictions.ilike("name", "Iz%"))
 * 	.add(Restrictions.gt("weight", new Float(minWeight)))
 * 	.addOrder(Order.asc("age"));
 * 
 * 
 * @see Criteria#createCriteria()
 * @see com.github.antelopeframework.mybatis.criterion.Restrictions
 * @see com.github.antelopeframework.mybatis.criterion.Order
 * @see com.github.antelopeframework.mybatis.criterion.Criterion
 * 
 * @author yangzhi.yzh
 */
@Getter
public class Criteria implements Serializable {
	private static final long serialVersionUID = 1L;

	private final List criterionEntries = new ArrayList();
	private final List orderEntries = new ArrayList();
	
	private Integer maxResults = 0;
	private Integer firstResult = 0;
	
	private Criteria() {}
	
	/**
	 * Create {@link Criteria} instance
	 * 
	 * @return The criteria instance for manipulation and execution
	 */
	public static Criteria createCriteria() {
		return new Criteria();
	} 

	/**
	 * 是否为无条件查询; 无条件查询会对表进行全量查询, 极度损耗性能; 在findByCriteria方法时, 最好判断一下是否为无条件查询.
	 * 
	 * @return
	 */
	public boolean isNoConditionQuery() {
		return criterionEntries.size() == 0;
	}
	
	/**
	 * Add a {@link Criterion restriction} to constrain the results to be retrieved.
	 *
	 * @param criterion The {@link Criterion criterion} object representing the restriction to be applied.
	 * @return this (for method chaining)
	 */
	public Criteria add(Criterion expression) {
		add(this, expression);
		return this;
	}

	/**
	 * 如何理解hasValue:
	 * 
	 * 	String: {@link StringUtils#isNotBlank(CharSequence)}
	 * 	Object: not null
	 * 
	 * 
	 * @param expression
	 * @return
	 */
	public Criteria addIfHasValue(Criterion expression) {
		if (isValueValid(expression)) {
			this.add(expression);
		}
		
		return this;
	}
	
	/**
	 * Add an {@link Order ordering} to the result set.
	 *
	 * @param order The {@link Order order} object representing an ordering to be applied to the results.
	 * @return this (for method chaining)
	 */
	public Criteria addOrder(Order ordering) {
		orderEntries.add(new OrderEntry(ordering, this));
		return this;
	}
	
	/**
	 * 
	 * @param maxResults
	 * @return
	 */
	public Criteria setMaxResults(int maxResults) {
		if (maxResults > 0) {
			this.maxResults = maxResults;
		}
		
		return this;
	}
	
	public Criteria setFirstResult(int firstResult) {
		if (firstResult > 0) {
			this.firstResult = firstResult;
		}
		
		return this;
	}
	
	public Iterator iterateExpressionEntries() {
		return criterionEntries.iterator();
	}

	public Iterator iterateOrderings() {
		return orderEntries.iterator();
	}
	
	private Criteria add(Criteria criteriaInst, Criterion expression) {
		criterionEntries.add(new CriterionEntry(expression, criteriaInst));
		return this;
	}
	
	@Getter
	public static final class CriterionEntry implements Serializable {
		private static final long serialVersionUID = 1L;

		private final Criterion criterion;
		private final Criteria criteria;

		private CriterionEntry(Criterion criterion, Criteria criteria) {
			this.criteria = criteria;
			this.criterion = criterion;
		}

		@Override
		public String toString() {
			return criterion.toString();
		}
	}

	@Getter
	public static final class OrderEntry implements Serializable {
		private static final long serialVersionUID = 1L;

		private final Order order;
		private final Criteria criteria;

		private OrderEntry(Order order, Criteria criteria) {
			this.criteria = criteria;
			this.order = order;
		}

		@Override
		public String toString() {
			return order.toString();
		}
	}
	
	/**
	 * 
	 * @param criterion
	 * @return
	 */
	private static boolean isValueValid(Criterion expression) {
		if (expression == null) {
			return false;
		}
		
		if (expression instanceof Junction
				|| expression instanceof LogicalExpression
				|| expression instanceof SQLCriterion) {
			throw new UnsupportedOperationException();
		}
		
		if (expression instanceof SimpleExpression) {
			return isValueValid(((SimpleExpression) expression).getValue());
		}
		
		if (expression instanceof BetweenExpression) {
			BetweenExpression be = (BetweenExpression) expression;
			return isValueValid(be.getHi()) && isValueValid(be.getLo());
		}
		
		if (expression instanceof InExpression) {
			return isValueValid(((InExpression) expression).getValues());
		}
		
		if (expression instanceof LikeExpression) {
			return isValueValid(((LikeExpression) expression).getValue());
		}
		
		if (expression instanceof NotExpression) {
			return isValueValid(((NotExpression) expression).getCriterion());
		}
		
		if (expression instanceof NotNullExpression || expression instanceof NullExpression) {
			return true;
		}
		
		return true;
	}
	
	/**
	 * 
	 * @param v
	 * @return
	 */
	private static boolean isValueValid(Object v) {
		if (v == null) {
			return false;
		}
		
		if (v instanceof String) {
			StringUtils.isNotBlank((String) v); 
		}
		
		return true;
	}
	
	/**
	 * 
	 * @param values
	 * @return
	 */
	private static boolean isValueValid(Object[] values) {
		if (values == null || values.length == 0) {
			return false;
		}
		
		boolean hasValid = false;
		for (Object v : values) {
			if (isValueValid(v)) {
				hasValid = true;
				break;
			}
		}
		
		return hasValid;
	}
}